The invention is generally in the field of dentistry and concerns a method and system for acquiring a three-dimensional image of teeth geometry. In the following, the term "dental image" will be used to denote an acquired three-dimensional teeth image.
The term "partial dental image" will be used to denote an image of part of the teeth surface, e.g. an image of only the lingual surfaces of the teeth ("lingual image") or of only the buccal surfaces of the teeth ("buccal image"); the term "sectional dental image" will be used to denote an image of a section of the teeth, i.e. not including all the teeth.
The obtaining of a dental image is of importance for various dental, and particularly orthodontic procedures in order to make treatment decisions, e.g. design braces, crowns or the like, and to allow monitoring of an orthodontal treatment. Typically, in accordance with existing methods, a teeth impression in an appropriate matrix is obtained and from that a positive, typically plaster, teeth model is prepared. Such a teeth model can be stored as such, it can be photographed, it can be scanned and stored digitally in a computer, etc. Scanning and digitizing a three-dimensional teeth image is a relatively complex procedure. Various methods have been proposed involving direct scanning of teeth by probes which forms part of an imaging system fixed to the skull, but such procedures cannot easily be practiced in widespread use.
DE-A1-3810455, published on Oct. 5, 1989, discloses a system for acquiring a three-dimensional image of an irregular object, particularly teeth, which comprises an optic system consisting of an illuminator and an optical receiver, by scanning the teeth with the optic system, a three-dimensional image is obtained.
U.S. Pat. No. 4,935,635 of Jan. 19, 1990, discloses a three-dimensional measuring system intended particularly for use in acquiring a three-dimensional teeth object. The system has a laser diode which projects a triangulating beam at the surface of the object to be mapped, the beam scanning repeatedly across the surface. By triangulation, the X-axis, or the depth information is obtained and by correlating a particular point with a position of the scanner along the scan line gives the Y-axis information, i.e. information on the width's direction. The scanner and diode are mounted on a slide or platform which move in a "Y" axis in and out the mouth, driven by a stepper motor, and the monitored position of the stepper motor is coordinated with the other information on each spot to yield X-axis information.
Laurendeau, D., et al., IEEE Transactions on Medical Imaging, 10(3):453-461, New York, USA, 1991 discloses a computer vision technique for acquiring and processing of dental images. In accordance with this paper a standard three-dimensional teeth wax image is prepared and is optically scanned simultaneously in both sides whereby three-dimensional teeth image is obtained.
U.S. Pat. No. 5,237,988 of Aug. 24, 1993 discloses a three dimensional correlation of images of dental arcades, making use of an impression in the occlusive position, providing a reference in the form of three mutually spaced reference points. Three-dimensional views are taken of the impression and the points and views are also taken with the impression removed. Using the images of the reference points as a basis, the sets of views are then correlated to bring them into a single reference system.
EP-A1-634150 published on Jan. 18, 1995, discloses an aid for the production of a tooth or bridge. In accordance with this publication, a model is placed on a rotary holder and during rotation is scanned by an angled scanning device.